Objectives

After completing this section, you should be able to migrate virtual machines from one host to another within a cluster in the Red Hat Virtualization environment.

Virtual Machine Migration

Live migration refers to the process of moving a virtual machine from one physical host to another while it is running. The contents of memory, network configuration, and access to storage are moved from the original virtual machine on one physical host to a new virtual machine on a different physical host, which then replaces the old virtual machine. Live migration is useful to support maintenance tasks on hosts without disrupting running virtual machines.

Live migration is transparent to the end-user. The virtual machine remains powered on, and user applications continue to run, while the virtual machine is migrated to a new physical host. Clients communicating with the virtual machine should notice no more than a network pause of a few milliseconds as the transfer completes.

For live migration to work properly, the new host must have a CPU with the same architecture and features as the original host. Red Hat Virtualization helps manage this by organizing hosts into clusters. A virtual machine may only migrate to hosts that are members of its cluster. This helps ensure that virtual machines do not migrate between machines that support different sets of processor features.

Administrators must ensure that their Red Hat Virtualization environment is correctly configured to support live migration before starting a migration. Live migration of virtual machines requires the following configuration prerequisites:

Live migration is performed using the migration network. The default configuration uses the ovirtmgmt network as both the management network and the migration network. Although each live migration is limited to a maximum transfer speed, and there are a maximum number of migrations that may run concurrently, concurrent live migrations can saturate a network shared by management and migration traffic. For best performance, the storage, migration, and management networks should be separated to avoid network saturation.

Manually Migrating Virtual Machines

Red Hat Virtualization supports manual migration of a virtual machine between hosts associated with the same cluster. Migration can be triggered using the RHV-M Administration Portal. A virtual machine can be migrated to a specific host, or to a host that RHV-M automatically selects. Manual migration of a virtual machine requires administrative privileges.

The Compute → Virtual Machines menu option displays the Compute >> Virtual Machines page in the RHV-M Administration Portal. The Compute >> Virtual Machines page lists all the virtual machines. Each virtual machine is represented in a specific row. These rows use different columns to display properties of the virtual machines. One of these columns, the Host column, shows the host that contains the virtual machine.

Figure 9.1: Viewing the virtual machines

The Compute >> Virtual Machines page includes a Migrate button that triggers migration of the selected virtual machine. Clicking on the Migrate button opens the Migrate VM(s) window. The Migrate VM(s) window has a Destination Host field that allows you to select a specific destination host for the virtual machine. The default value of the Destination Host field is Automatically Choose Host, which causes the RHV-M to automatically decide the destination host for the virtual machine. The Migrate button in the Migrate VM(s) window is used to confirm the intention of migrating the selected virtual machine. After confirming the migration, the Status field of the virtual machine transitions through a series of values, including Migrating From: 0% and Migrating To, before finishing with a status of Up.

Figure 9.2: Selecting the destination host